Because material handling implements such as tractors, bulldozers, and the like must frequently be left unattended and unguarded at a job site, it is very desirable that such implements incorporate systems to prevent unauthorized operation and to deter theft. Material handling devices generally represent significant capital investment and all reasonable precautions must be taken to prevent the equipment from being operated by vandals or thieves who might gain access to the equipment. While storage of the equipment in suitably locked sheds or garages is of course desirable, structures of this nature are ordinarily not available at a construction or job site, and thus by necessity the equipment must frequently be left relatively unprotected.
While most types of material handling implements include lockable ignition systems for their internal combustion engines to prevent unauthorized operation, it must be recognized that a determined thief might be able to bypass the ignition system lock. Therefore, the present invention contemplates a hydraulic system for such implements which acts to maintain the implement in an immobile state, and thus prevents the implement from being moved even in the event that the engine of the implement is started.